Irradiation campaign in EOLE reactor facility of fibre Bragg grating sensors dedicated to the online temperature measurement in critical reactor facilities (SOMETIME project)
Résumé
Within the framework of the renovation of the MASURCA research reactor [1], the development of the future instrumentation for physics measurements has to come along with a better control of the conditions in which they are performed. One of the main goals is to improve the mastery
of temperature effects that affects all reactivity measurements. The assessment of the temperature correction coefficient actually suffers from a large uncertainty (~20%, k=2) due to the difficult establishment of the average temperature representative of the core fuel part. Increasing the number
of temperature measurement points, currently limited to less than 20, is clearly part of the solution. Due to some set-up constraints specific to the MASURCA facility, the use of miniature sensors allowing quasi-distributed temperature measurements without perturbing the experiments seems promising candidates. In addition to their sensing performances (1°C of precision for a temperature range going from 20°C to 100°C), these temperature sensors must withstand the radiation environments associated with MASURCA that mainly consists in a moderate neutron fluence (up to 1014n/cm²).
Based on the feedback obtained in previous studies [2-6] achieved in more severe conditions (higher temperature and high neutron and gamma fluences), and taking advantage of the framework of the NEEDS [7] initiative, CEA and CNRS/LabHC have decided to start the SOMETIME project
dedicated to the design and the qualification of in-core and on-line quasi-distributed temperature measurements systems based on optical fibre Bragg grating sensors (FBG). This kind of sensor will enable online centimetric temperature profiles monitoring using a single optical fibre, thus allowing to minimize both the intrusivity and the induced thermal perturbation in the fuel element compared to the dozen of thermocouples required to get today’s the same profile.
In this paper we present the NEEDS initiative, the overall context and the objectives of this project, together with the experimental set-up used in the EOLE facility [8]. Several kinds of FBG temperature transducers have been characterized during a preliminary testing campaign performed in
EOLE reactor (2014): their evolution during the irradiation (few 1013n/cm²) is described with a specialfocus on the Bragg wavelength shift with respect to the neutron fluence. Finally, we detail the coming work for the second part of the SOMETIME project which will be dedicated to qualify the
functionality of a representative FBG temperature instrumentation together with the challenging task of FBG arrays packaging and insertion within a real MASURCA fuel element.
[1] W. AssaI, J.C. Bosq, F. Mellier “Experimental Measurements at the MASURCA Facility” First International Conference on Advancements in Nuclear Instrumentation Measurement Methods and their Applications (ANIMMA), Print ISBN - 978-1-4244-5207-12009 IEEE
[2] S. Girard, Y. Ouerdane, A. Boukenter, C. Marcandella, J. Bisutti, J. Baggio, and J-P. Meunier, “Integration of Optical Fibers in Radiative Environments: Advantages and Limitations”, IEEE Transactions on Nuclear Science, vol. 59 (4), pp. 1317 – 1322, 2012.
[3] A. Morana, S. Girard, E. Marin, C. Marcandella, P. Paillet, J. Périsse, J.-R. Macé, A. Boukenter, M. Cannas and Y. Ouerdane, "Radiation tolerant fiber Bragg gratings for high temperature monitoring at MGy dose levels", Optics Letters, Vol. 39, No. 18, September 15, 2014
[4] G. Cheymol, A. Gusarov, B. Brichard; "Fibre Optic Extensometer for High Radiation and High Temperature Nuclear applications”; IEEE transactions on nuclear science, Vol.60, N°.5, October 13.
[5] G. Laffont, R. Cotillard and P. Ferdinand, Multiplexed regenerated Fiber Bragg Gratings for high temperature measurement, Measurement Science and Technology, Vol. 24, N° 9, 24, 2013
[6] G. Laffont, R. Cotillard and P. Ferdinand, “9000 hours-long high temperature annealing of regenerated fibre Bragg gratings”, 5th European Workshop on Optical Fibre Sensors, Krakow, Poland,May 19-22, 2013
[7] NEEDS French Research Framework – « Nuclear, Energy, Environment, Waste and Society” http://www.cnrs.fr/mi/spip.php?article19
[8] J.-C. Bosq, M. Antony, J. Di Salvo, J.-C. Klein, N. Thiollay, P. Blaise, P. Leconte., “The Use of EOLE and MINERVE Critical Facilities for the Generation 3 Light Water Reactor Studies”, Proc. Int. Conf. ICAPP, Nice, May 2-5, 2011